Chemical process



Patented Apr. 23, 1946 Frank J. Soday, Swarthmore, Pa., assignor to The United Gas Improvement Company, a corporation oi Pennsylvania No Drawing.

Application September 5, 1942, Serial No. 457,475

9 Claims. (Cl. 260-681.5)

This invention is concerned with the removal of impurities from unsaturated hydrocarbons.

More particularly, this inventionis concerned with the removal of impurities from unsaturated hydrocarbons and unsaturated hydrocarbon fractions by th application of metals in group Ia and group He of the periodic table and certain active alloys or derivatives thereof.

It is an object of the present invention to continuously purify unsaturated hydrocarbon fractions, and particularly diolefine fractions by treatmentin a continuous system with one or more alkali or alkaline earth metals, or active alloys or derivatives thereof, under carefully cdntrolled conditions. Another object of the invention is the provision of certain methods whereby unsaturated hydrocarbon fractions and particularly diolefine fractions-may be purified in a continuous manner by the application of alkali or alkaline earth metals without undue loss of unsaturated hydrocarbons, in the form of soluble or insoluble polymers. Other objects and advantages of the invention will be apparent to those skilled in the art upon an inspection of the following description and claims.

Unsaturated hydrocarbons and unsaturated hydrocarbon fractions, particularly the latter, frequently contain substantial quantities of im-' purities, such as acetylenic compounds; oxygenated compounds such as aldehydes and peroxides; and the like; which interfere with the use of such materials in most, if not all, industrial applications.

Thus, diolefines and diolefine fractions, par- ,ticularly the latter, frequently contain substantial quantities of acetylenes, such as monovinyl or other acetylene, oxygenated compounds such as aldehydes and peroxides, as well as certain other impurities. 7

As an example, a 50% light oil butadiene fraction obtained by the pyrolysis of petroleum in the gas phase at temperatures substantially above 1300 F., followed by condensation 'and fractionation, was found to contain 1.0% of acetylenes,

This butadiene frachave discovered that unsaturated hydrocarbons and unsaturated hydrocarbon fractions, particularly dioleflne fractions, may bereflned in a continuous manner by the application in finely divided form of at least one metal of group Ia and group 11a of the periodic table, as well as certain active alloys or derivatives thereof. Particularly desirable results are obtained by the use of finely divided alkali and alkaline earth metals.

Examples of such metals are lithium, sodium, potassium, rubidium, caesium, barium, strontium and calcium. Due to. the availability and low cost of sodium and potassium, however, these metals are preferred for the use set forth herein.

Alloys of these metals, such as NaPbm, NaHg4, NaCas, NaZnm, XML, and the like, also may be employed for the removal of undesired impurities from unsaturated hydrocarbons and unsaturated hydrocarbon fractions. In general, the alloys of the respective metals react with the impurities present in such hydrocarbons and hydrocarbon fractions at a slower rate thanthe corresponding metals.

Compounds of these metals which may be emfor refining diolefines and diolefine fractions.

Such diolefines and diolefine fractions may be obtained from any desired source such as synthetically, for example by the removal of the elements of chlorine or hydrogen chloride from polychlorinated C4 compounds, by the partial hy drogenation of monovinylacetylene, by the dehydrogenation of butanes and/or butylenes, and by the dehydration of C4 alcohols and glycols; by

the pyrolysis of petroleum andpetroleum hydro carbons, such as by the pyrolysis of petroleum in the gaseous phase at temperatures above 1000 F., and more particularly above 1300" F., followed by condensation and'fractionation; and by thepyrolysis of other materials, such as by the pyrolysis of cyclohexane or by the pyrolysis of alcohols,

such as the pyrolysis of ethyl alcohol. In the latter case, the process may include a combination oi' dehydrating and/or pyrolytic reactions. Thus. it may be carried out by passing the alcohol at suitable temperatures over suitable catalytic agents, such as for example alumina and the like, followed by secondary pyrolysis. or recombination steps, if desired. Other procedures also may be employed for the production of butadiene or butadiene fractions which may be refined by the methods to be more particularly described herein.

The diolefine or diolefine fractions also may be initially concentrated to any desired extent prior to refining, and such concentration may be carried out by any desired method. This may include concentration by fractionation, azeotropic distillation, solvent extraction, a combination of solvent extraction and fractionation methods. and a the formation of complexes between the diolefine and some active compound, such as cuprous chloride, followed by the removal of the non-diolefine portion of the fraction and the decomposition of the complex. Other concentrating methods also may be employed if desired.

In addition, other refining methods also may be applied to diolefines and diolefine fractions to remove at least a portion or one or more impurities present prior to refining by methods to be more particularly described herein. Thus, such fractions may be contacted with acids or acidic solutions or materials to remove a portion of certain impurities or undesirable materials present. Thus, light oil butadiene fractions may be contacted with sulfuric acid to remove at least a portion of the isobutylene present.

Such concentrating and/or partial refining op- 'erations also may be applied to the diolefine or diolefine fractions subsequent to the'refining operations to be more particularly described herein. I find that a solution of sodium, or a suspension or emulsion of very finely divided sodium, or a solution, suspension, or emulsion of one or more sodium alloys or active compounds, is a particularly desirable agent for the continuous removal of certain undesirable impurities from unsaturated hydrocarbons and unsaturated hydrocarbon fractions, and particularly from diolefines and diolefine fractions. Excellent results are obtained by the use of a suspension of very finely divided sodium.

The refining method disclosed herein diflers fundamentally from all methods described heretoiore for the refining of unsaturated hydrocarbons or unsaturated hydrocarbon fractions in that the material in question is treated with a meta] of group Ia or groupIIa, or an active alloy or compound of such metals, in finely divided or solution form in a continuous system. By the use of a, continuous system, the loss of valuable hydrocarbons due to side reactions or to polymerization' is very markedly reduced, or almost completely eliminated.

This is of particular importance in the case of diolefines. such as butadiene, which are quite susceptible to polymerization when placed in contact with certain active metals, as well as active alloys and derivatives thereof. Thus, sodium is a very active catalyst for the polymerization of butadiene and is employed for this purpose in several industrial processes, notably in Russia. The use of this material in 'very finely divided form for the refining of butadiene, therefore, must be carried out within well defined limits in order to prevent undue loss of butadiene due to polymeria zation. The success of the refining method employing finely divided sodium, or other active metals, alloys, or compounds, must be attributed largely to the continuous nature of operation, re-

sulting ina minimum contact time between the butadiene and the reactant.

Although the process may be carried out in any desired manner, I prefer to conduct it in a vertical vessel or tower in which a certain height of a liquid suspension or solution of the active refining agent is maintained. The material to be refined then is passed upward through this column of liquid at a rate sufficient to insure the removal of the desired quantity and type of impuritiespresent at the temperature employed.

Other methods of contacting the material to be treated and the refining agent also may be employed if desired. Thus, the unsaturated hydrocarbon may be passed through a horizontal treating unit, such as a pipe or bank of pipes, containing a suspension of the desired refining agent, or otherwise.

The suspending liquid employed, for the refining agent may be of any desired type, provided that it does not .react with the reagent or the material to be treated to any substantial extent, and provided that it does not introduce any additional impurities into the material to be treated. I find that hydrocarbons and-hydrocarbon fractions of lesser unsaturation are particularly desirable materials for use as suspending medium for refining agents of the type described herein. Excellent results have been obtained by the use of aromatic hydrocarbons and aromatic hydrocarbon fractions for this purpose.

It is to be understood, of course, that the material treated dissolves to some extent in the suspending medium, consequently the suspending medium actually employed in the operation of the process usually comprises a mixture oi. the material to be treated and the suspending medium initially introduced into the system. Thus, in the treatment of a light oil butadiene fraction with a xylene suspension of finely divided sodium in a continuous system operating at 50 C. and atmospheric pressure, the suspending medium contained 11% of the butadiene fraction by weight after equilibrium-conditions had been established.

In a similar manner, when refining a light oil butadiene fraction in a continuous system with a'xylene suspension of finely divided sodium at 50 C. and a pressure of 50 pounds per square inch, gauge, the composition of the suspending medium after equilibrium conditions had been establlshed was 76% butadiene fraction and 24% xylene.

The material being treated also may serve as a suspending medium for the refining agent without the addition of any other material, if desired. Thus, alight oil butadiene fraction may be introduced into the desired tower 'or vessel. together with the finely divided refining agent, after which the butadiene fraction is passed into the suspension of the refining agent in the butadiene fraction at the desired temperature, the charging rate and more particularly the operating pressure being adjusted 'to maintain the treating agent at the desired level in the vessel.

It is to be understood, of course, that'the portion or the .material to be treated which has been dissolved in the suspending medium or which has been employed as the suspending medium in the substantial absence of other liquid materials, does not remain in the treating zone throughout the entire treating cycle. Rather, this material is in a state of dynamic equilibrium with the material being treated, a portion of it volatilizing continuously and being removed from 2,898,810 the system, the material volatilized in this manner being replaced by the solution of a corresponding quantity of freshly added material to be treated. The major portion of the material to be treated, of course, bubbles up through the suspending medium without dissolving therein.

The thickness of the layer of reagent through which the material to be treated is preferably passed depends upon a number of factors, such as the quantity and type of impurities present, the extent to which such impurities are to be removed, the type and degree of dispersion of the treating agent employed, the reaction temperature, the concentration of the treating agent I in the suspending medium, and the like. In general, howeveryI prefer to employ a layer of reagent at least one foot thick and, more preferably, at least two feetthick. Excellent results are obtained by the use of a layer of reagent at least four feet thick.

It will be recognized that, other things being equal, the depth of reagent employed in the treating vessel controls the contact time between the material to be refined and the refining reagent.

The degree of dispersion of thetreating agent also has a very profound effect upon the degree I of refining obtained. In the case of sodium, I

prefer to employ a subdivided mass in which at least the majority of the particles present have a diameter of not more than 0.05 and, more preferably, not more than 0.03". sults are obtained when at least the majority of the particles present have a diameter of not more than 0.02".

This subdivision may be carried out in any desired manner. Thus, in the case of sodium, solution of this material in liquid ammonia may be introduced into an inert liquid, such as xylene, at room temperature or atelevated temperatures. of the ammonia present results in the dispersion of the sodium present in the xylene in an extremely finely divided state. Another method comprises spraying molten sodium into an inert liquid such as xylene or solvent naphtha. By suitable variations in the type and degree of fineness and/or dispersing ability of the spray nozzle employed, sodium of almost any desired degreev of fineness may be obtained at will.

Another satisfactory method comprises melting the sodium under the surface of a suitable liquid, such as xylene, followedby violent agitation, such as with a turbo-mixer, and cooling with agitation. Other methods which may be used include extrusion through fine orifices, and the generation of an are between sodium electrodes in an inert liquid. I

Although almost any desired concentration of treating agent in the suspending medium may be employed, depending upon the type and concentration of the fractionto be refined, the tem perature, the depth of reagent employed, and the like, I generally prefer to employ, a reagent containing less than 30%, and more particularly less than 20%, by weight of the treating agent. Excellent results are obtained when less than 15% by weight of the treating agent is suspended in'the suspending medium.

It is to be understood, of course, that the term suspending medium refers to the actual suspending agent employed during the treating operation, and includes any of material being treated which may dissolve in such agent.

The type .and'concentration of the unsaturated Excellent re- The almost instantaneous volatilization hydrocarbon or unsaturated hydrocarbon fraction to be treated also has a considerable iniiuence upon the method of operating the process. Thus, with a highly concentrated butadiene, such as 98% butadiene, the reagent should preferably contain a fairly low concentration of active agent to minimize losses due to pclymeriza- I generally prefer to employ a fraction of such concentration, and with such proportion of sus-' pending medium, that the actual concentration of unsaturated hydrocarbon, such as butadiene, in the reaction zone is less than and, more preferably, less than 70%. Excellent results are obtained when the actual concentration of unsaturated hydrocarbon in the reaction zone is less than 60%.

The process maybe carried out at any desired pressure, such as atmospheric, subatmospheric, and superatmospheric pressures.

The temperature at which the process is conducted also has a very considerable bearing upon the degree to which'the fraction is refined and the losses incurred due to polymerization. Although the optimum reaction temperature to be employed is dependent largely uponother factors, such as the concentration of both the unsaturated hydrocarbon and the refining agent in the reaction zone, I generally prefer to conduct the refining operations at temperatures below 100 C. and, more particularly, below 80 C. Excellent results are obtained by conducting the refining operations at temperatures below 70 C.

The rate at which the material to be refined is passed through the reagent has a very considerable effect upon the degree to which the impurities present are removed, although this is dependent to some extent upon other variables such as the concentration of refining agent in the suspending medium and the temperature at which the refining operations are being conducted. While it is difiicult to establish exact limits for optimum throughputs under all conditions, I generally prefer not to exceed a throughput of material to be treated on an hourly basis of more than four times the weight of suspending medium employed and more preferably, not more than twice the weight of the suspending medium. Excellent results are obtained when not more than equal quantities of material to be treated, upon passed through the suspending medium.

It will be recognized that the contact time between the material tobe treated and the reagent is determined both by the thickness of the layer of reagentemployed and by the rate at which the material'to be treated is passed through the reagent.

The method employed for introducing the material to be refined into the refining agent also has some influence upon the extent to which the unsaturated hydrocarbon or unsaturated hydrocarbon fraction is refined. In general, it may be said that a line stream or jet of theliquid or gaseous material to be refined is desired. This may be accomplished by introducing the material to be treated into the reagent by means of suitable orifices, jets, nozzles, or other subdividing means. Porous objects or materials also may be employed for this purpose, such as porous ceramic or glass difiusing blocks or units.

As the refining agent may show some tendency to settle out in the bottom of-the treating vessel or unit, the jets or nozzles by means of which the material'to betreated is introduced into the unit division; the refining operations until may be so arranged as to prevent any undue settling of this material. In vertical vessels. this may be accomplished by locating these units in such a way asto impinge the inlet stream or streams upon the bottom of the treating vessel. The inlet iets also may be arranged tangentially to impart a swirling or circular motion to the treating reagent, if desired. Another method comprises locating the inlet Jet or Jets directly in the bottom of the reactor, or tangentially in the sides of the reactor, or both, to prevent any settling in the bottom of the reacting vessel and/or to impart any desired circular or other motion to the treating medium.

Any desired combination oi these methods also may be employed, such as the use of a Jet or jets directly impinging upon the bottom of the reactor in conjunction with the use of a tan ential jet or jets to prevent the active agent from settling out and depositing on the walls of the reactor and/or to maintain the reaction medium in any desired state of agitation.

The reaction medium also may be maintained in the desired degree of agitation by the use of suitable stirring or mixing devices, or by the use of circulating pumps, or by a combination of these methods, or otherwise. One or more of these methods also may be used in conjunction with one or more of the methods discussed previously to maintain the system in the desired degree of dispersion.

It should be pointed out, however, that the use of such agitation methods is not required in most cases. Thus, excellent results have been secured by conducting the refining operations in a tower, the material to be treated being introduced into the bottom of the tower by means of a small orifice. The passage of the fraction being treated in the gaseous state upward through the column was found to maintain the system in the desired degree of agitation.

The refining agent, particularly when finely divided sodium is employed for this purpose, usually acts both as a reactant and as a polymerizing agent for the removal of undesired impurities. Thus, in the case of light oil butadiene fractions containing monovinylacetylene, other acetylenes, aldehydes, and other oxygenated imurities, the sodium will react with at least a portion of the 'monovinylacetylene present to form sodium inonovinylacetylide, and may react with certain of the oxygenated derivatives to form corresponding derivatives. At least a portion of the acetylenic hydrocarbon present also are Polymerized to form polymers, or copolymers with other unsaturated hydrocarbons present, which frequently are insoluble in nature. Certain of the oxygenated derivatives, such as aldehydes,' also may be polymerized to form polymers which may be insoluble in type.

As a. result, the refining of butadiene fractions with a suspension of finely divided sodium is characterized by the gradual accumulation of insoluble polymers in the refining medium. This 65' may be removed in any desired manner, such as by filtration, which may be carried out continuously during the refining operation, or may be carried out in a batchwise manner after the termination of the refining step.

As the removal of the insoluble polymers also is attended by some loss of refining agent, even when the latter is in a very fine state of subit is advisable in many cases to continue the refining agent r. I has been largely or completely exhausted before filterin The solid or semi-solid filtered products may he treated to recover any desired materials or they may be disposed of in any suitable manner. Thus, any unchanged refining agent, such as sodium, may be recovered by melting and coalescing operations, or by amalgamation with mercury, or otherwise. Certain of the reaction products, such as sodium monovinyl acetylide and/or other metallic acetylides, may be decomposed with water to regenerate the corresponding acids or they may be reacted with carbon dioxide to form unsaturated acids, or otherwise.

A convenient method for the disposal of the insoluble polymers comprises treatment with carbon dioxide, suitably in the presence of traces of moisture, followed by filtration.

,As the cost of the treating process is largely a function of the quantity of the reactive agent employed in the refining operations, the efficient utilizationof such agent is of considerable importance. A desirable method for insuring optimum utilization of the treating agent is to carry out the operations in a continuous countercurrent manner, the reagent moving through the system in a manner countercurrent to that of the material to be treated.

This may be illustrated by means of a consideration of a simple continuous countercurrent system comprising two treating towers or vessels. The material to be treated is passed into the first tower, which contains a partially exhausted reagent. This serves to remove a substantial portion of the impurities present, after which the partially refined material passes into the second tower, which contains a fresh, or more highly concentrated, reagent. This serves to remove the impurities present to the desired extent. The process is continued until the reagent in the first tower is almost, or completely, exhausted, after which it is discarded and the partially exhausted reagent from the second column substituted for it. Fresh reagent then is added to the second column.

In this manner the material to be treated and the treating agent pass through the system countercurrent to each other, the first continuously and the second in a discontinuous manner.

This may be modified such as by the continuous addition of fresh reagent to the second tower, the continuous transfer of partially exhausted reagent to the first tower, and the continuous withdrawal of more completely exhausted, or exhausted, re-

agent from the first tower. .A completely continuous countercurrent treating system thus is achieved.

Any desired modification of these methods may be employed, and any number of treating towers or units may be used. It will be observed that in each of the cases discussed, the incoming material to be refined is contacted with partially exhausted reagent (maximum concentration of impuritiesminimum concentration of reagent), while the outgoing. material to be refined is contacted with fresh or more highly concentrated reagent (minimum concentration of impurities-maximum concentration of reagent). Thus the two objectives to be sought, namely, practically complete, 01' complete, utilization of the reagent and substantial, or practically complete, removal of impurities from the material to be refined, are achieved.

. As the limiting factor affecting the utilization of the reagent is the proportion -ofinsoluble polymers and/orv residues which can be contained t xylene and 11% butadiene fraction.

tobe treated therethrough, it frequently happens a that the quantity of insoluble material present is insufiicient to interfere seriously with the operation of the process when the refining agent present has been almost completely exhausted. In this case, the operation of the unit ma be continued by the addition thereto of anadditional quantity of the refining agent, and this. process may be continued until the concentration of insoluble material in the reagent renders it too a viscous to be used further in the process in'a satisfactory manner.

In thi connection, it is well to point out that the insoluble products formed during the reaction have a tendency to stabilize the sodium suspension and act to reduce the rate of settling of the finely divided sodium in certain cases. As this is desirable, the incomplete removal of insoluble products from the reagent may be indicated, or even the addition of a certain quantity of such materials to a fresh reagent.

Soluble poLvmers also usually are formed in small amounts during the refining operations. As certain of these soluble and/or liquid polymers are converted on prolonged contact with the refining agent to viscous and/or insoluble products, their removal from the suspending medium, suitably at the end of a refining cycle and prior to the return of the suspending agent to the system, may

be indicated. n the other hand, certain of these soluble polymers are sufiiciently stable to act as a suspending medium for the refining agent.

The process may be more completely illustrated by means of the following examples.

Example 1 prepared by agitation of molten sodium under the surface of xylene by means of a turbo-mixer, followed by cooling with continuous agitation. Under the operating conditions employed, the actual refining medium comprised a 10% sodium suspension in a suspending medium containing 89% The height of refining reagent employed was /2 feet.

The refining operation was continued for a period pf 30 hours, the butadiene fraction being charged at the rate of approximately 900 grams per hour. At the end of this period the apparent divided. sodium employed was 130 grams representing a 7% suspension in the indicated sus- P nding medium. I

. The run was continuedifor a total of 31 hours at an average charging rate of 838 grams per.

hour, the total quantity of butadiene fraction charged being 24,319 grams.

The refined butadiene fraction contained only 0.023% acetylenes and 0.00% aldehydes. The quantity of soluble polymers produced was 29 grams, or approximately 01% by weight of the total fraction refined.

The impurities present, particularly theacetylenes'and the aldehydes were converted both' to sodium derivatives and to insoluble polymers. of the 130 grams of sodium charged to the unit, 31 grams were recovered in unchanged form.

Onlysmall quantities of the butadiene fraction treated was lost during the treating process in the form of polymers, and otherwise.

In the specification and in the claims, the following terms have the indicated meanings.

The term a metal of group Ia and group 11a of the periodic system" is intended to include lithium, sodium, potassium, rubidium, caesium, barium, strontium, and calcium, as well as active alloys or compounds containing one or more of such metals as an essential ingredient;

The term "finely divided is intended to mean a material reduced to such'a state of fineness that the preponderating part is composed of particles having a diameter of less than 0.05", as well as materials in the colloidal or dissolved form,

While reagents and procedures of a particular nature have been specifically described, it is to be understood that these are given by way of illustration. Therefore, changes, omissions, additions,

substitutions, and/or modifications may be made within the scope of the claims without departing from the spirit of the invention, which is intended to be limited only as required by the prior art.

I claim:

l. A process for refining diolefini hydrocarbon material contaminated with impurity including acetylenic material comprising passing said contaminated hydrocarbon material at a temperature below 100 C. through a dispersion of a finely divided metal selected from the group consisting of metals of group Ia and group IIa ofthe periodic system, said dispersion being at least one foot in thickness in the direction of fiow of said co'ntaminatedhydrocarbon material and containconcentration of unchangedsodium in the total Example 2 A 50% light oil butadiene fraction containin 1.0% acetylenes and 0.04% aldehydes, was passed continuously into the bottom of a 2" steel colsuspending medium (89% xylene-11% butadiene me less than 30% by weight of said finely'divided metal, maintaining the concentration of said diolefinic hydrocarbon material in the reaction zone less than 80% by weight of the total material present, while maintaining the rate of fiow perhour of said contaminated hydrocarbon material through said dispersion at less than four times the weight of dispersion medium employed, and removing saiddiolefinic hydrocarbon material less contaminated with impurity including acetylenic material from said reaction zone sufficiently rapidly to prevent a large loss of said diolefinic hyumn containing a xylene suspension of very finely divided sodium at a temperature of 50 C. and a pressure of 50 pounds per square inch, gauge. Under the operating conditions employed, the

actual suspending medium was a mixture of 433 grams (24%) of xylene and 1367 grams (76%) oi the butadiene fraction. The quantity of finely drocarbon material due to the polymerization thereof.

2. A process for refining a diolefinec'ontained in admixture with impurity including acetylenic material in a light oil diolefine fraction which comprises continuously passing said fraction at a temperature below 80 0. through a dispersion of a finely divided metal selected from the group consisting of metals of group Iaand group Ha of the periodic system, said dispersion containing less than 20% by weight thereof'of said finely divided metal and being at least two feet in thickness in the direction of fiow of said admixture, maintaining the concentration oi said diolefine in the reaction zone less than 10% by weight of the total material present, while maintaining a rate of flow per hour of said fraction through said dispersion of less than twice the weight of dispersion medium employed, and continuously removing said diolefine fraction less contaminated with impurity including acetylenic material from said reaction zone sufllciently rapidly to prevent a large loss of said diolefine due to polymerization thereof.

3. A process for the recovery of butadiene from a mixture containing the same and containing impurity including acetylenic material which comprises continuously passing said mixture at a temperature below 80 C. through a dispersion of a finely divided metal selected from the group consisting of metals of group Ia and group 110 of the periodic system, said dispersion containing less than 20% by weight thereof of said finely divided metal and being at least two feet in thickness in the direction of fiow otsaid mixture, maintaining the concentration of said butadiene in the reaction zone less than 70% by weight of the total material present, while maintaining a rate of fiow r hour of said mixture through said dispersion of less than twice the wei ht of dispersion medium employed, and continuously removing said butadiene less contaminated with impurity including acetylenic material from said reaction zone sufilciently rapidly to prevent a large loss of said butadiene due to polymerization thereof.

4. A process for the recovery of a diolefine from .a mixture containing the same and containing impurity including acetylenic material which comprises continuously passing said mixture in vapor phase under temperature conditions below 100 C. through a dispersion of a finely divided metal selected from the group consisting of metals per hour of said mixture through said dispersion at less than four times the weight of dispersion medium employed, and continuously removing said diolefine less contaminated with impurity including acetylenic material from said reaction zone sufliciently rapidly to prevent a large loss of said diolefine due to polymerization thereof.

5. A process for the recovery of butadiene from a mixture containingthe same and containing impurity including acetylenic material which comprises continuously passing said mixture in vapor phase under temperature conditions below 80 C. through a dispersion of a finely divided agssasro.

in vapor phase less contaminated with impurity including acetylenic material from said reaction zone sufliciently rapidly to prevent a large loss of said butadiene due to polymerization thereof.

6. A process for the purification of butadiene contained in admixture with impurity including acetylenic material which comprises continuously passing said admixture in vapor phase at a temperature below 80 C. through a reaction zone containing a dispersion of finely divided alkali metal, said dispersion containing less than 20% by weight thereof of saidfinely divided alkali metal and being at least two feet in thickness in the direction of flow of said admixture, maintaining the concentration of said butadiene in said reaction zone less than 70% by weight of the total material present, while maintaining a rate of fiow per hour of said admixture through said dispersion of less than twice the weight of dispersion medium employed, and continuously removing butadiene in vapor phase less contaminated with impurity including acetylenic material from said reaction zone sufilciently rapidly to prevent a large loss of said butadiene due to polymerization thereof.

L A process for the purification of butadiene contained in admixture with impurity including acetylenic material which comprises continuously passing said admixture in vapor phase at a temperature below 100 C. through a dispersion of finel divided sodium, said dispersion bein at least one foot in thickness in the direction of flow of said admixture and containing less than 30% by weight thereof of said finely divided sodium, maintaining the concentration of said butadiene in the reaction zone less than 80% by weight of the total material present while maintaining the rate of flow per hour of said admixture through said dispersion at less than four times the weight of dispersion medium employed, and continuously removing butadiene in vapor phase less contaminated with said impurity including acetylenic material from said reaction zone sulficiently rapidly to prevent alarge loss of said butadiene due to polymerization thereof.

8. A process for the recovery of butadiene from a mixture containing the same and containing impurit including acetylenic material which comprises continuously passing said mixture in vapor phase at a temperature below 100 0. through a reaction zone containing a dispersion of finely divided sodium at least the majority of the particles of which have a diameter of not more than 0.05 inches, said, dispersion containing metal selected from the group consisting of metals of group Ia and group 11a of the periodic system, said dispersion containing less than 20% by weight thereof of said flnely'dlvided metal and being at least two feet in thickness in the direction of-flow of said mixture, maintaining the i concentration of butadiene in the'reaction zone less than 70% by weight of the total material present, while maintaining a rate of flow per hour of said mixture through said dispersion of less than twice the weight of dispersion medium employed, and continuously removing butadiene less than 30% by weight thereof of said finely divided sodium and being at least one foot in thickness in the direction of flow of said mixture, maintaining the concentration of said butadiene in said reaction zone less than by weight of the total material present, while maintaining a rate of flow per hour of said mixture through said dispersion of less than four times the weight of dispersion medium employed, and continuously removing butadiene in vapor phase and less contaminated with said impurity including acetylenic material from said reaction zone sumciently rapidly to prevent a large loss of said butadiene due to polymerization thereof. 1

9. A process for the purification of a light oilbutadiene fraction containing butadiene together with impurity at least a'portion of which is in the form of acetylenic material which comprises continuously passing said fraction in vapor phase at a temperature below 80 C. upwardly through a reactionzone containing a dispersion of finely divided sodium at least the majority of the particles of which have a diameter of not more than 0.03 inches, said dispersion containing lessthan' 20% by weight thereof of said finely divided sodium and being at least two feet in thickness in the direction of fiow ofsaid fraction, maintaining the concentration of said butadiene in said reaction zone less than 70% by weight of the total material present,'while maintaining a rate of flow per hour of said fraction through said dispersion of less than twice the weight of dispersion 

